Liquid crystal display panel

ABSTRACT

A liquid crystal display panel comprising a liquid crystal cell with liquid crystals sealed therein, sandwiched between two transparent substrates having an electrode on each of the inner surfaces thereof facing each other, a first polarizing film disposed on the visible side of the liquid crystal cell, a second polarizing film disposed on the opposite side of the liquid crystal cell from the visible side, and a light absorbing film disposed on the opposite side of the second polarizing film from the visible side. The first polarizing film is a reflection-type polarizing film reflecting the light linearly polarized in the direction orthogonal to the transmission axis thereof, and the second polarizing film is an absorption-type polarizing film or color polarizing film each absorbing the light linearly polarized in the direction orthogonal to the transmission axis thereof. A transflective reflector and/or a color filter may preferably be disposed between the second polarizing film and a light source.

TECHNICAL FIELD

The invention relates to a liquid crystal display panel used in variouselectronic equipment such as timepieces (watches and clocks), portableinformation equipment, and so forth for indicating time information,calendar information and other various information.

BACKGROUND TECHNOLOGY

A timepiece for indicating digital display of time information such ashour, minute, and second, and calendar information such as date, days ofthe week, month, and year, by use of a liquid crystal display panel(device), has been in widespread use for watches and clocks, providedwith a crystal oscillation circuit.

There has also been in use a combination watch wherein analog displayindicating time information by the hands of the watch is used incombination with digital display indicating time information andcalendar information in numbers and letters.

Further, there has been proposed an analog watch for selectivelydisplaying scales in various patterns, or for displaying simulated handsfor an hour hand, a minute hand, and a second hand, by making up thedial thereof based on a liquid crystal display panel (refer to, forexample, Japanese Patent Laid-open S54-153066).

A liquid crystal display panel, small in size and consuming very littleelectric power, has been in widespread use as a display panel fordisplaying necessary information (character information and graphicinformation) in various electronic equipment other than timepieces, suchas cellular phones, desktop electronic computers, portable game players,and so forth.

In such a liquid crystal display panel, a liquid crystal cell filledwith liquid crystals is sandwiched between two transparent substrateshaving an electrode on respective inner surfaces thereof, facing eachother, and an upper polarizing film and a lower polarizing film aredisposed, respectively, on the external surface of the transparentsubstrates, on the opposite sides. If an electric field is applied tothe liquid crystals by applying a voltage to a pair of electrodes on thetransparent substrates which hold the liquid crystal cell therebetween,the optical property of the liquid crystals is changed, thereby locallycontrolling transmission and absorption of light falling on the liquidcrystal display panel such that a predetermined display is effected.

Either of the upper polarizing film and the lower polarizing film in theconventional liquid crystal display panel is a polarizing film absorbingthe light linearly polarized in the direction orthogonal to thetransmission axis thereof. Accordingly, light falling on the liquidcrystal display panel is controlled to transmit though the twopolarizing films or to be absorbed by either of the polarizing films,and there seen is a portion that appears light owing to direct lightfrom a light source or a reflected light when the incident light isreflected on a reflection film, or a portion that appears black becauseof the interception of the incident light.

In the case of a watch using the conventional liquid crystal displaypanel described above, time information and calendar information aredisplayed in white against the black background in normally-black modewhen displaying using a back-light illuminated by a light sourceincorporated therein.

However, in the case of displaying digital information of time and soforth in the liquid crystal display panel, the area of a region(background part) other than the area of the information display part isvery large. Accordingly, when indicating digital display of timeinformation and calendar information in white against the blackbackground, light absorbed by the polarizing film is predominantcompared with light that is actually used in display. Accordingly, mostof the light emitted by the light source is wasted.

Accordingly, it is necessary to increase the amount of luminescence todisplay with high visual recognition, leading to an increase of thepower consumption, causing a problem of shortening the life span of abattery, in the case of portable electronic equipment.

Further, in the panel merely indicating digital display of timeinformation and calendar information in white against the blackbackground, variation in design cannot be offered, with a tendency toquickly lose popularity among consumers. Probably as a result,consumption of digital watches has recently been on the decline. Neithercombination watches nor analog watches with a liquid crystal displaypanel has since received market acceptance.

Similarly, in the case of transmission display by the light sourceincorporated therein with the conventional liquid crystal display panelused in other electronic equipment, various information expressed inletters and graphics is generally displayed in white against the blackbackground, and although there are some wherein information can bedisplayed in black against the white background in an inverse mode, theliquid crystal display panel has been found still lacking in designvariation and sense of amusement.

In light of the present situation as described, the present inventionhas been developed, and an object of the invention is to provide aliquid crystal display panel capable of indicating sufficiently visibledisplay even at dark locations where no or little external light isavailable, and offering novelty and variation in design while ensuring along service life of a battery used therein.

SUMMARY OF THE INVENTION

To this end, a liquid crystal display panel according to the inventioncomprises a liquid crystal cell with liquid crystals sealed therein,sandwiched between two transparent substrates having an electrode oneach of the inner surfaces thereof facing each other, a first polarizingfilm disposed on the visible side of the liquid crystal cell, a secondpolarizing film disposed on the opposite side of the liquid crystal cellfrom the visible side thereof, and a light source disposed on theopposite side of the second polarizing film from the liquid crystalcell, and is characterized in that the first polarizing film is areflection-type polarizing film reflecting the light linearly polarizedin the direction orthogonal to the transmission axis thereof, and thesecond polarizing film is an absorption-type polarizing film absorbingthe light linearly polarized in the direction orthogonal to thetransmission axis thereof.

With the liquid crystal display panel constructed as above, when lightemitted from the light source goes out to the visible side after beingtransmitted through the second polarizing film, the liquid crystal cell,and the first polarizing film, display in white is indicated, however,if the light transmitted through the liquid crystal cell is linearlypolarized in the direction orthogonal to the transmission axis of thefirst polarizing film, the linearly polarized light can not betransmitted through the first polarizing film, and no light is allowedto go out to the visible side, indicating display in black. In thiscase, as the first polarizing film is a reflection-type polarizing film,the linearly polarized light reaching the first polarizing film isreflected at parts for display in black (including the background part),and returned to the light source after passing through the liquidcrystal cell and the second polarizing film again.

The light returned to the light source will have its direction ofpolarization disturbed while undergoing reflection and scatteringrepeatedly within the light source, and be approximate to circularlypolarized light, going out again from the light source to fall on thesecond polarizing film to be utilized for display.

Accordingly, even with a light source having a smaller quantity of lightemission than that in the case of the conventional liquid crystaldisplay panel, bright display with sufficient visibility can beexecuted. As a result, the life of a battery can be prolonged due toreduction in consumption of power supplied by the battery.

Further, by stalling a non-reflection layer on the visible side of thefirst polarizing film, a quantity of light reflected by the firstpolarizing film can be held down at a low level even at locations suchas the outdoors at daytime, and so forth, where an intense externallight falls, maintaining excellent visibility.

Then, if a transflective reflector or an optical diffusing layer isinstalled between the light source and the second polarizing film, ahalf of the external light falling on the first polarizing filmpropagates to the liquid crystal cell, a half again of which istransmitted through the liquid crystal cell, and absorbed by the secondpolarizing film (absorption-type polarizing film) in the background partand parts for display in black.

In parts for display in white, light transmitted through the liquidcrystal cell passes through the second polarizing film as it is, onlyabout a half of which is reflected by the transfective reflector andsent out to the visible side via the second polarizing film, the liquidcrystal cell, and the first polarizing film.

In such a case, therefore, display of information can be executed withthe use of reflected external light only by turning off the power supplyto the light source, achieving significant savings in consumption of abattery in use.

Further, by use of a color polarizing film for the second polarizingfilm, or by installing a color filter between the light source and thesecond polarizing film, parts for display in white can be indicated incolors differing from the color of light emitted by the light source,enabling a display of information which is highly variable in the toneof color to be effected.

By installing the transflective reflector film between the light sourceand the second polarizing film, and further, the color filter betweenthe transflective reflector film and the light source, it becomespossible to change the tone of color of the display executed with theuse of external light from that using light emitted from the lightsource, enabling the display highly variable in the tone of color to beeffected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a typical sectional view showing the construction of a liquidcrystal display panel according to a first embodiment of the invention,and

FIG. 2 is an enlarged sectional view of the liquid crystal cell, and

FIG. 3 is a plan view of display segments of the liquid crystal cellshowing a pattern thereof by way of example;

FIG. 4 is a view for explaining the display function of the liquidcrystal display panel shown in FIG. 1, and

FIG. 5 is a view for explaining the display function of a conventionalliquid crystal display panel;

FIGS. 6 to 10 are respectively typical sectional views showing theconstruction of the liquid crystal display panel according to second tosixth embodiments of the invention; and

FIG. 11 is an external perspective view of a wrist watch to which theliquid crystal display panel of the invention is applied, and

FIG. 12 is a view showing the inner structure of the wrist watch in FIG.11.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of a liquid crystal display panel according to theinvention will be described in detail hereinafter with reference to theattached drawings.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment: FIGS. 1 to 5

First, a first embodiment of a liquid crystal display panel according tothe invention is described with reference to FIGS. 1 to 5.

FIG. 1 is a typical sectional view showing the construction of theliquid crystal display panel, and FIG. 2 is an enlarged sectional viewof a liquid crystal cell incorporated therein, showing a fragmentarysectional view omitting a lengthwise midsection thereof. FIG. 3 is aplan view of display segments of the liquid crystal cell showing apattern thereof by way of example.

The liquid crystal display panel 10 shown in FIG. 1 is made up of theliquid crystal cell 1, a first polarizing film 2 disposed on the visibleside (the upper side in the figure) from a viewer, a second polarizingfilm 3 disposed on the side (the underside in the figure) of the liquidcrystal cell 1, opposite from the visible side, and a light source 4disposed on the side of the second polarizing film 3, opposite from theliquid crystal cell 1.

As shown in FIG. 2, the liquid crystal cell 1 comprises two glasssubstrates 11, 12, and liquid crystals 13 sandwiched between the twoglass substrates so as to be sealed in with sealing agents 14, and atwisted nematic (TN) liquid crystal having a twist angle, for example,90° is used for the liquid crystals 13.

Transparent electrodes 15, 16 (opposing electrode and display electrode)made of indium tin oxide (ITO), are formed on the inner faces of the twoglass substrates 11, 12, respectively, on the side in contact with theliquid crystals 13, and alignment treatment is further applied to theinner face of the respective transparent electrodes, in contact with theliquid crystals 13, such that liquid crystal molecules are aligned in apredetermined direction.

At least one of the electrode 15 and the electrode 16 of the liquidcrystal cell 1 is formed in a pattern of multiple display segments 17for indicating numbers shown in FIG. 3, and the alignment condition ofthe liquid crystals 13 held between the transparent electrodes 15, 16,is altered by applying a voltage between the transparent electrodes 15,16, thereby indicating various information in digital display in abackground part 18 by the interaction between the first and secondpolarizing films 2 and 3.

The first polarizing film 2 shown in FIG. 1 is a sheet-shaped memberwhich transmits the light linearly polarized in the direction parallelwith the transmission axis thereof, and reflects the light linearlypolarized in the direction orthogonal to the transmission axis thereof,and it is called as reflection-type polarizing film.

As the sheet-shaped reflection type polarizing film (reflection-typepolarizing sheet), an optical film, DBEF (trade name), manufactured byMinnesota Mining and Manufacturing Co., U. S. A., is used for. The samecan be obtained from Sumitomo Three M Co., Ltd., in Japan.

The reflection-type polarizing film as described above has beendeveloped by the manufacturer described and is disclosed in detail in JP(PCT) H9-507308A (International Publication No.: WO95/17691) and JP(PCT) H9-511844A (International Publication No.: WO95/27919).

Meanwhile, the second polarizing film 3 is a sheet shaped-member whichtransmits the light linearly polarized in the direction parallel withthe transmission axis thereof, and absorbs the light linearly polarizedin the direction orthogonal to the transmission axis thereof, and it isa common absorption-type polarizing film.

The reflection-type polarizing film as the first polarizing film 2 andthe absorption-type polarizing film as the second polarizing film 3 arearranged in a manner such that the transmission axes thereof are inparallel with each other.

The light source 4 is a back-light that employs an electroluminescence(EL) element, a light-emitting diode (LED) array, a cold cathode tube,or a hot cathode tube or etc.

Now display functions of the liquid crystal display panel 10 aredescribed with reference to FIGS. 4 and 5.

When the light source 4 is lit up, a half of light emitted therefrom andfalling on the second polarizing film 3 (absorption-type polarizingfilm) is absorbed thereby while the rest of the light is turned to thelight linearly polarized in the direction parallel with the transmissionaxis of the absorption-type polarizing film, and falls on the liquidcrystal cell 1.

In parts of the display segments 17 shown in FIG. 3, where display is tobe indicated in white, the liquid crystals 13 lose the twisting functionthereof by the agency of an electric field when a voltage is appliedbetween the electrodes 15, 16 of the liquid crystal cell 1, shown inFIG. 2, and consequently, linearly polarized light falling thereonreaches the first polarizing film (reflection-type polarizing film) 2without the direction of polarization being rotated when passingtherethrough.

Accordingly, since the linearly polarized light has the polarizingdirection parallel with the transmission axis of the first polarizingfilm 2, the same propagates to the visible side after being transmittedthrough the first polarizing film 2 as it is as shown by the directionof the arrow A in the left half part of FIG. 4. Therefore, if the lightsource 4 emits white light, display in white is indicated.

Meanwhile, in the background part 18 shown in FIG. 3, and in parts ofthe display segments 17, where display is to be indicated in black,linearly polarized light falling on the liquid crystal cell 1 has thepolarizing direction rotated by 90 degrees by the liquid crystals(twisted nematic liquid crystals) 13 when passing therethrough since novoltage is applied between the electrodes 15, and 16 of the liquidcrystal cell 1 shown in FIG. 2, and it is turned to the light linearlypolarized in the direction orthogonal to the transmission axis of thefirst polarizing film 2 upon reaching there.

Accordingly, the linearly polarized light is reflected by thereflection-type polarizing film, which is the first polarizing film 2,as shown by the direction of the arrow B in the right half part of FIG.4, and returned to the light source 4 via the liquid crystal cell 1 andthe second polarizing film 3. Therefore, no light is sent out to thevisible side, indicating display in black.

The light returned to the light source 4 will have the direction ofpolarization approximate to that of circularly polarized light whileundergoing reflection and scattering repeatedly within the light source,and propagate again from the light source 4 to the second polarizingfilm 3 so as to be reused for display as described in the foregoing.Thus, with this liquid crystal display panel , the light propagatingfrom the light source 4 to the background part, and parts of the displaysegments for display in black, is reflected by the reflection-typepolarizing film, that is, the first polarizing film 2, and sent back tothe light source 4 so as to be reused.

By contrast, with the conventional liquid crystal display panel shown inFIG. 5, an absorption-type polarizing film has been adopted for a firstpolarizing film 2′ disposed on the visible side of the liquid crystalcell 1. Accordingly, as shown in the left half part of the figure,display in white is indicated in the same way as in the case of theliquid crystal display panel according to the invention, however, whendisplay in black is indicated as shown in the right half part of thefigure, the light linearly polarized in the direction orthogonal to thetransmission axis of the first polarizing film 2′ after passing throughthe liquid crystal cell 1 (as shown by the arrow B) is completelyabsorbed by the first polarizing film 2′, that is, the absorption typepolarizing film, not to be utilized again for display.

As is evident from the foregoing, with the liquid crystal display panel10 according to the invention, it is possible to display timeinformation and so forth with sufficient brightness even if a lightemission quantity of the light source 4 is far smaller than that for theconventional liquid crystal display panel. Therefore, electric powerconsumed by the light source 4 is significantly reduced, enabling theservice life of a battery as a power supply source to be prolongedconsiderably.

Also, with the use of a light source having the intensity of lightsimilar to that for the conventional liquid crystal display panel,clearer and brighter display can be indicated.

It is needless to say that the invention can be applied not only to theliquid crystal display panel to indicate digital display by allowing atleast one of the electrodes 15, and 16 of the liquid crystal cell 1 toform in a seven segment pattern of multiple display segments forindicating numbers but also to a liquid crystal display panel toindicate vanous letters and figures by allowing at least one of theelectrodes 15,16 of the liquid crystal cell 1 to form in dot-matrixtype.

A case where the liquid crystals sealed in the liquid crystal cell aretwisted nematic (TN) liquid crystals having a twist angle of 90° or lesscausing linearly polarized light passing therethrough to undergo phasemodulation has been described in the foregoing by way of example,however, supertwisted nematic (STN) liquid crystals having a twist angleof 90° or more may be used instead.

Further, the reflection-type polarizing film, that is, the firstpolarizing film 2, and the absorption-type polarizing film, that is, thesecond polarizing film 3, holding the liquid crystal cell 1 interposedtherebetween, may be disposed such that respective transmission axescross each other at an angle equivalent to the twist angle of the liquidcrystal cell 1 (90 degrees in the case where twisted nematic liquidcrystals having a twist angle of 90° are used for the liquid crystals ofthe liquid crystal cell 1). In such a case, parts where no voltage isapplied to the liquid crystals are displayed in white while parts wherea voltage is applied to the liquid crystals are displayed in black.

Second to Sixth Embodiments: FIGS. 6 to 10

Now, second to sixth embodiments of a liquid crystal display panelaccording to the invention are described with reference to FIGS. 6 to10.

FIGS. 6 to 10 are typical sectional views showing the constructions of aliquid crystal display panel used in carrying out various embodiments ofthe invention similar to FIG. 1, parts corresponding to those previouslydescribed with reference to FIG. 1 are denoted by the same referencenumbers, and description thereof is omitted.

Constructions and operations of the respective embodiments set forthhereunder other than these explained individually are the same as thoseof the liquid crystal display panel of the aforementioned firstembodiment.

Second Embodiment:

FIG. 6 shows the construction of a liquid crystal display panelaccording to the second embodiment of the invention.

As in the case of the liquid crystal display panel 10 shown in FIG. 1,this liquid crystal display panel is provided with the first polarizingfilm 2, that is a reflection-type polarizing film, and the secondpolarizing fibn 3, that is an absorption-type polarizing film,respectively, with the liquid crystal cell 1 interposed therebetween,and the light source 4 is provided at the side opposite to the liquidcell 1 of the second polarizing film 3.

The liquid crystal display panel has an absorption-type polarizing filmto which non-reflection treatment is applied and which is disposed onthe surface of the first polarizing film 2 at the visible side as anon-reflection layer 5.

The reflection-type polarizing film, that is, the first polarizing film2 has the optical property of reflecting the light linearly polarized inthe direction orthogonal to the transmission axis thereof. With theliquid crystal display panel as shown in FIG. 1, therefore, at alocation such as the outdoors in fine weather, where a very intenseexternal light falls, a half of the external light falling on the firstpolarizing film 2 is reflected toward the visible side with the possibleresult that contrast between parts displayed in white by lighttransmitted from the light source 4, and the background part as well asparts displayed in black is caused to deteriorate, causing the displayto become difficult to see for a viewer.

With the second embodiment of the liquid crystal display panel accordingto the invention, shown in FIG. 6, however, reflection of external lightfalling on the first polarizing film 2 toward the visible side isprevented by the non-reflection layer 5, thereby enabling display whichis in good contrast and can be easily seen even at locations where anintense external light falls.

In the second embodiment, an absorption type polarizing film withnon-reflection coating applied on the surface thereof on the visibleside is used for the non-reflection layer 5. However, the non-reflectionlayer 5 need not be a polarizing film, and any non-reflection sheetcapable of absorbing light reflected by the reflection-type polarizingfilm may be used for this purpose. Further, the same effect can beobtained by applying non-reflection coating on the surface of the firstpolarizing film 2, on the visible side, instead of using anon-reflection sheet

Third Embodiment:

FIG. 7 shows the construction of a third embodiment of a liquid crystaldisplay panel according to the invention.

The liquid crystal display panel according to this embodiment isprovided with a reflection type polarizing film as a first polarizingfilm 2 disposed on the visible side of a liquid crystal cell 1, a colorpolarizing film 6 as a second polarizing film disposed on the side ofthe liquid crystal cell 1, opposite from the visible side thereof, and alight source 4 disposed on the external side of the color polarizingfilm 6.

The color polarizing film 6 is a sheet prepared by mixing coloringmaterial into or dispersing pigments into an absorption-type polarizingfilm such that all components of light, in specific colors (at givenwavelengths), are transmitted therethrough, while the light linearlypolarized in the direction orthogonal to the transmission axis of thecolor polarizing film and being among components of light in othercolors (at other wavelengths) is absorbed.

With this liquid crystal display panel, display in colors differing fromthe color of light emitted by the light source 4 can be indicated by theagency of the color polarizing film 6 provided on the light source 4side of the liquid crystal cell 1, enabling a display of informationwhich is highly variable in color and excellent in design to beattained.

For example, in case of using the liquid crystal display panel in atimepiece, it is possible to display time display regions and calendardisplay regions in different colors with the use of different colorpolarizing films among the display region, so that a timepiece superiorin design quality can be provided.

With the liquid crystal display panel according to the third embodimentas well, a non-reflection layer 5 is preferably installed on the visibleside of the first polarizing film 2 as with the case of the secondembodiment shown in FIG. 6 so as to prevent reflection of external lightfalling on the first polarizing film 2 toward the visible side. By sodoing, display in good contrast and easy for a viewer to see can beindicated even at locations where an intense external light falls.

Fourth Embodiment

FIG. 8 shows the construction of a fourth embodiment of a liquid crystaldisplay panel according to the invention.

This liquid crystal display panel is made up by installing a colorfilter 7 between the absorption type polarizing film, that is, thesecond polarizing film 3, and the light source 4 in the liquid crystaldisplay panel (the first embodiment of the invention) shown in FIG. 1.

With such a liquid crystal display panel as described, display in colorsdiffering from the color of light emitted by the light source 4 can beindicated by the agency of the color filter 7, enabling display ofinformation, highly variable in color and excellent in design quality,to be effected.

In this case, a sheet-shaped color filter as the color filter 7 isdisposed throughout the surface of the second polarizing film 3.However, in the case of using the liquid crystal display panel in, forexample, a timepiece, it is possible to display a time display regionand a calendar display region in different colors either by disposingthe color filter 7 differentiated in color among corresponding displayparts, or by use of different color filters for respective displayregions, thereby providing a timepiece excellent in design quality.

With the liquid crystal display panel shown in FIG. 8, the color filter7 is disposed between the light source 4 and the second polarizing film3, however, a location where the color filter 7 is to be disposed is notlimited to the above. For example, the color filter 7 may be disposed onthe visible side of the first polarizing film 2 instead. If the colorfilter 7 is disposed throughout the surface of the first polarizing film2, on the visible side thereof, the same beneficial effect as that forthe second embodiment can be obtained since reflection of light by thefirst polarizing film 2 toward the visible side can be prevented.

Further, although the sheet-shaped color filter may be used as the colorfilter 7, the color filter 7 may be printed on the glass substrate 11 or12, making up the liquid crystal cell 1 (refer to FIG. 2), or on thefirst polarizing film 2 or the second polarizing film 3. If the colorfilter 7 is formed by printing on the glass substrate 11 or 12, the samecan be formed with high precision in relation to the display segments 17shown in FIG. 3, facilitating display to be indicated in fine detail.

Fifth Embodiment:

FIG. 9 shows the construction of a fifth embodiment of a liquid crystaldisplay panel according to the invention.

This liquid crystal display panel is assembled with a transflectivereflector 8 between the absorption-type polarizing film, that is, thesecond polarizing film 3 and the light source 4 in the liquid crystaldisplay panel (the first embodiment of the invention) shown in FIG. 1.

When the liquid crystal display panel according to the fifth embodimentof the invention is in use at a location such as outdoors in fineweather, where a very intense external light falls on the display, theexternal light falling thereon is transmitted through a first polarizingfilm 2, a liquid crystal cell 11, and the second polarizing film 3, thenreflected by the transflective reflector 8, and travels out along theoptical path in reverse order toward the visible side, indicatingdisplay in white. In such a case, therefore, display of information canbe executed without the use of light emitted from the light source 4, byturning off the power supply for the light source 4. On the other hand,at a dark location such as the indoors and so forth, where aninsufficient external light falls on the display, display is executedwith light emitted from the light source 4 by turning on the powersupply for the light source 4.

Accordingly, consumption of power from a battery is reduced, enablingthe life of the battery to be prolonged.

The same beneficial effect will be obtained by forming an opticaldiffusing layer in place of the transflective reflector 8 on the lightemitting surface of the light source 4 or the surface of the secondpolarizing film 3, where emitted light falls.

Otherwise, between the color polarizing film 6 and the light source 4 asshown in the third embodiment in FIG. 7, the transfiective reflector 8,or the optical diffusing layer may be installed.

Sixth Embodiment:

FIG. 10 shows the construction of a sixth embodiment of a liquid crystaldisplay panel according to the invention.

This liquid crystal display panel is assembled with a color filter 7between the transfiective reflector 8 and the light source 4 in theliquid crystal display panel (the fifth embodiment of the invention)shown in FIG. 9.

With the liquid crystal display panel according to this embodiment aswell, when same is in use at a location such as outdoors in fineweather, where a very intense external light falls on the display, theexternal light falling thereon which is transmitted through a firstpolarizing film 2, a liquid crystal cell 1, and a second polarizing film3 is then reflected by the transflective reflector 8, and travels outalong the optical path in reverse order toward the visible side,indicating display in white. In such a case, therefore, display ofinformation can be executed without the use of light emitted from thelight source 4, by turing off the power supply for the light source 4.

On the other hand, at a dark location such as the indoors and so forth,where an insufficient external light falls on the dosplay, display isexecuted by turning on the power supply for the light source 4. In thiscase, light emitted from the light source 4 is transmitted through thecolor filter 7, and consequently, light outgoing toward the visible sideis a light component only at a specific wavelength (in a specific color)determined by the color filter 7.

Accordingly, it is possible to change the tone of color of the displayobserved with the use of external light from that observed using lightemitted from the light source 4, so that an electronic device superiorin design quality can be provided.

In this case as well, the same beneficial effect can be obtained byforming an optical diffusing layer in place of the transflectivereflector 8 on the upper surface of the color filter 7 or on theunderside surface of the second polarizing film 3.

Application Example of Liquid Crystal Display Panel According to theInvention:

Described next is an example of a digital wrist watch in which theliquid crystal display panel that has been explained hitherto isapplied. FIG. 11 is a perspective view showing an external appearance ofthe wrist watch and FIG. 12 is a sectional view showing the internalconstruction of the wrist watch.

A case 20 of the wrist watch is assembled with a glass 22 and a caseback 23, integrally joined with a case body 21 made of metal.

The glass 22 is made of a transparent material such as sapphire glass,tempered glass, or plastic, and is integrally joined with the front faceof the case body 21 by means of direct bonding, or fitting therein via apacking. The case back 23 is integrally joined with the back face of thecase body 21 by means of screwing therein or fitting therein via apacking. Thus, the case 20 has an airtight inner structure so as not toallow ingress of dust or moisture.

A liquid crystal display panel (liquid crystal display device) 10according to the invention to serve as a display for indicating time andso forth is installed on the side of the glass 22 inside the case 20.

The liquid crystal display panel 10 comprises a time display section 10a for displaying hour, minute, and second, a calendar display section 10b for displaying month, date, days of the week, and a colon mark displaysection 10 c for blinking every second. These display sections areformed by segment patterns of the transparent electrodes 15, 16 that areformed on the inner surfaces of the glass substrates 11, 12 of theliquid crystal cell 1 shown in FIG. 2.

Further, the liquid crystal display panel 10 is capable of displaying afunction of time display for 12 consecutive hours or 24 consecutivehours in a usual fashion, an alarm function, a stopwatch function, atimer function, and so forth.

Changeover among such various functions and correction of time areexecuted by manipulating a plurality of switching buttons 24 installedin the side of the case body 21 of the case 20. A packing is providedbetween each of the switching buttons 24 and the case body 21 so as notto allow ingress of dust and moisture into the case 20.

As shown in FIG. 11, the watch has the inner structure such that theliquid crystal display panel 10 and a printed circuit board 30 aredisposed substantially in parallel with each other inside the case 20,and a battery 31 serving as a driving power source of the printedcircuit board 30 is installed on the case back 23 side of the printedcircuit board 30.

A semiconductor integrated circuit 33 comprising a crystal oscillator 32having an oscillation frequency of 32,768 Hz, a crystal oscillationcircuit for generating a predetermined signal by oscillating the crystaloscillator, a frequency divider circuit, a driving circuit for drivingthe liquid crystal display panel 10, a central processing unit (CPU) foroverall control of the quartz watch, and so forth are mounted on theprinted circuit board 30.

The liquid crystal display panel 10 is electrically connected with theprinted circuit board 30 via a zebra rubber connector 34 disposedtherebetween. The zebra rubber connector 34 is disposed so as to becompressed thickness-wise in order to ensure electrical connectionbetween the liquid crystal display panel 10 and the printed circuitboard 30.

The zebra rubber connector 34 is made up of electrically conductivelayers, comprised of insulating silicone rubber with carbon and metalparticles contained therein, is formed at a predetermined pitch, and iselectrically conductive in the direction of thickness thereof via therespective electrically conductive layers, but in a transverselyinsulated condition between adjacent electrically conductive layers. Aconnection terminal pattern is formed on the faces of the liquid crystaldisplay panel 10 and the printed circuit board 30, opposite to eachother, respectively, in such a fashion as to correspond to verticallyconductive parts formed of the electrically conductive layer of thezebra rubber connector 34, and insulation parts of the zebra rubberconnector 34, alternately disposed, and in dimensions at the same pitchas that for the vertically conductive parts.

With the wrist watch, when pressing either of the switching buttons 24,the light source 4 of the liquid crystal display panel 10 is lit up sothat light transmitted through the liquid crystal display panel 10 andemitted by the light source 4 can indicate digital display of timeinformation such as time, minute, and second, and calendar informationsuch as date, days of the week, month, and year in white or variousother colors, against the black background.

Conversely, display condition can be inversed between the backgroundpart and the information display part so that time information, calendarinformation and so forth can be displayed in black against white orarbitrary colored background. FIG. 11 shows the display condition.

Any of the liquid crystal display panels described hereinbefore in thefirst to the sixth embodiments may be used as the liquid crystal displaypanel 10.

INDUSTRIAL UTILIZATION

As described in the foregoing, with the liquid crystal display panelaccording to the invention, the reflection-type polarizing filmreflecting the light linearly polarized in the direction orthogonal tothe transmission axis thereof is disposed on the visible side of theliquid crystal cell.

Accordingly, light emitted from the light source for backlighting andshining on non-display regions and parts for display in black isreturned to the light source and put to reuse.

For this reason, a light source having a smaller quantity of lightemission than before, that is, consuming less power than in the case ofthe conventional liquid crystal display panel, will suffice forobtaining display in brightness on the same order as that in theconventional case. Or, by use of a light source having power consumptionon the same order as in the conventional case, brighter display withvisibility superior to the conventional case can be effected.

Furthermore, by disposing the color polarizing film, the color filter,the transflective reflector, or the optical diffusing layer in place ofthe absorption type polarizing film between the liquid crystal cell andthe light source, it is possible to provide a liquid crystal displaypanel superior in design quality and capable of indicating colorfuldisplay or a liquid crystal display panel capable of indicating displayby reflection of external light.

Accordingly, if the liquid crystal display panel according to theinvention is applied to use as the display panel for timepieces andvarious other portable electronic equipment, the life of a batterytherein can be prolonged due to lower power consumption, and at the sametime, an electronic equipment superior in design quality and capable ofindicating display which is brighter and easily seen by a viewer can beprovided.

What is claimed is:
 1. A liquid crystal display panel comprising: aliquid crystal cell with liquid crystals sealed therein, sandwichedbetween two transparent substrates having an electrode on each of theinner surfaces thereof, facing each other; a first polarizing filmdisposed on a visible side of the liquid crystal cell; a secondpolarizing film disposed on the side of the liquid crystal cell,opposite from the visible side thereof; and a light source disposed onthe side of the second polarizing film, opposite from the liquid crystalcell; wherein at least one of the electrodes is formed in a pattern ofdisplay segments or in a dot-matrix type for indicating information,only one polarizing film is disposed on each side of the liquid crystalcell, and the first polarizing film is a reflection-type polarizing filmreflecting the light linearly polarized in a direction orthogonal to atransmission axis of the first polarizing film while the secondpolarizing film is an absorption-type polarizing film absorbing thelight linearly polarized in a direction orthogonal to a transmissionaxis of the second polarizing film.
 2. A liquid crystal display panelaccording to claim 1, wherein a non-reflection layer is installed on thevisible side of the first polarizing film.
 3. A liquid crystal displaypanel according to claim 2, wherein the non-reflection layer is a sheethaving a non-reflection surface thereon.
 4. A liquid crystal displaypanel according to claim 1, wherein a transflective reflector isinstalled between the second polarizing film and the light source.
 5. Aliquid crystal display panel according to claim 1, wherein an opticaldiffusing layer is installed between the second polarizing film and thelight source.
 6. A liquid crystal display panel according to claim 1,wherein a color filter is installed between the second polarizing filmand the light source.
 7. A liquid crystal display panel according toclaim 1, wherein a transflective reflector and a color filter areinstalled between the second polarizing film and the light source.
 8. Aliquid crystal display panel according to claim 1 wherein the firstpolarizing film and the second polarizing film are disposed such thatthe transmission axes thereof run in parallel with each other.
 9. Aliquid crystal display panel according to claim 1 wherein liquidcrystals causing linearly polarized light transmitted therethrough toundergo phase modulation or intensity modulation are sealed in theliquid crystal cell.
 10. A liquid crystal display panel according toclaim 9, wherein the liquid crystals are twisted nematic liquidcrystals.
 11. A liquid crystal display panel according to claim 9,wherein the liquid crystals are supertwisted nematic liquid crystals.